U.S. patent application number 13/449150 was filed with the patent office on 2012-12-13 for electrochromic device.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Kazuya Miyazaki, Shinjiro Okada, Kenji Yamada.
Application Number | 20120314272 13/449150 |
Document ID | / |
Family ID | 47295687 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120314272 |
Kind Code |
A1 |
Yamada; Kenji ; et
al. |
December 13, 2012 |
ELECTROCHROMIC DEVICE
Abstract
There is provided an EC device having stability against redox
reaction cycles, high transparency, i.e., the EC device does not
absorb light in the visible region in a bleached state, and having
excellent response speed. The electrochromic device includes a pair
of electrodes and a composition arranged between the pair of
electrodes, the composition containing an electrolyte and an
organic electrochromic compound, in which the organic
electrochromic compound includes an electrochromic portion that
exhibits electrochromic properties and an aromatic ring directly
bonded to the electrochromic portion, the electrochromic portion
forms one conjugated plane, an atom of the aromatic ring and
adjacent to an atom bonded to the electrochromic portion has a
substituent having a volume equal to or larger than the volume of a
methyl group, and a cathodically electrochromic organic compound is
further contained in addition to the organic electrochromic
compound.
Inventors: |
Yamada; Kenji;
(Yokohama-shi, JP) ; Okada; Shinjiro;
(Kamakura-shi, JP) ; Miyazaki; Kazuya; (Tokyo,
JP) |
Assignee: |
CANON KABUSHIKI KAISHA
Tokyo
JP
|
Family ID: |
47295687 |
Appl. No.: |
13/449150 |
Filed: |
April 17, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2011/080201 |
Dec 27, 2011 |
|
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|
13449150 |
|
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Current U.S.
Class: |
359/265 |
Current CPC
Class: |
C07D 409/04 20130101;
C07D 495/14 20130101; C07D 491/056 20130101; C07D 277/56 20130101;
C07D 333/16 20130101; C07F 7/0816 20130101; G02F 1/1516 20190101;
C07D 495/04 20130101; G02F 1/1503 20190101; C07D 333/32
20130101 |
Class at
Publication: |
359/265 |
International
Class: |
G02F 1/155 20060101
G02F001/155 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 7, 2011 |
JP |
2011-127678 |
Sep 22, 2011 |
JP |
2011-206999 |
Claims
1. An electrochromic device comprising a pair of electrodes and a
composition arranged between the pair of electrodes, the
composition containing an electrolyte and an organic electrochromic
compound, wherein the organic electrochromic compound includes an
electrochromic portion that exhibits electrochromic properties and
an aromatic ring directly bonded to the electrochromic portion, the
electrochromic portion forms one conjugated plane, an atom of the
aromatic ring and adjacent to an atom bonded to the electrochromic
portion has a substituent having a volume equal to or larger than
the volume of a methyl group, and the pair of electrodes has an
interelectrode distance of 150 .mu.m or less.
2. The electrochromic device according to claim 1, wherein the
organic electrochromic compound is an anodically electrochromic
organic compound.
3. The electrochromic device according to claim 2, wherein the
organic electrochromic compound further comprises a cathodically
electrochromic organic compound.
4. The electrochromic device according to claim 1, wherein the
longest absorption wavelength of the electrochromic portion is
longer than the longest absorption wavelength of the aromatic
ring.
5. The electrochromic device according to claim 1, wherein the HOMO
of the electrochromic portion lies higher than the HOMO of the
peripheral portion.
6. The electrochromic device according to claim 1, wherein the
electrochromic portion contains a thiophene ring.
7. The electrochromic device according to claim 1, wherein the
aromatic ring is a benzene ring.
8. The electrochromic device according to claim 1, wherein the
substituent on the aromatic ring is an electron-donating group.
9. The electrochromic device according to claim 8, wherein the
electron-donating group on the aromatic ring is an alkoxy
group.
10. The electrochromic device according to claim 1, wherein the
organic electrochromic compound is an anodically electrochromic
organic compound that has absorption in the visible range when
oxidized.
11. An optical filter comprising the electrochromic device
according to claim 1 and a switching device.
12. A lens unit comprising the optical filter according to claim 11
and an image pickup optical system.
13. An image pickup apparatus comprising an image pickup optical
system, the optical filter according to claim 11, and an image
pickup device configured to pick up an image through the optical
filter.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of International Patent
Application No. PCT/JP2011/080201, filed Dec. 27, 2011, which
claims the benefit of Japanese Patent Application No. 2011-127678
filed Jun. 7, 2011 and No. 2011-206999 filed Sep. 22, 2011, which
are hereby incorporated by reference herein in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a novel electrochromic
device.
BACKGROUND ART
[0003] There has been active development of electrochromic
(hereinafter, also abbreviated as "EC") devices including
electrochromic materials in which optical absorption properties,
such as colored states and optical transmittances of materials, are
changed by electrochemical redox reactions.
[0004] PTL 1 discloses an EC device in which a conductive polymer
is formed on a transparent electrode and in which an electrolytic
solution is enclosed between the electrode and a counter electrode.
PTL 2 discloses a solution-phase EC device in which an electrolytic
solution containing a low-molecular-weight molecule, such as
viologen, dissolved therein is enclosed between a pair of
electrodes.
[0005] For the conductive polymer described in PTL 1, an EC layer
can be directly formed on the electrode by the electrolytic
polymerization of a monomer. Known examples of the conductive
polymer that forms the EC layer include polythiophene, polyaniline,
and polypyrrole.
[0006] In the case where such a conductive polymer is
electrochemically oxidized or reduced, the .pi.-conjugated chain
length of a main chain is changed, thereby changing the electron
state of the highest occupied molecular orbital (HOMO). Thus, a
wavelength absorbed by the conductive polymer is changed.
[0007] These conductive polymers absorb light in the visible region
in the electrically neutral state and thus are colored. Oxidation
of these conductive polymers allows wavelengths absorbed by the
conductive polymers to shift to longer wavelengths.
[0008] In the case of the shift of the wavelengths to the infrared
region, the polymers do not exhibit absorption in the visible
region, so that the EC device is bleached.
[0009] Meanwhile, for the EC material containing the viologen-based
compound described in PTL 2, dications are dissolved in the
solution in a bleached state. Viologen is converted into radical
cations by a reduction reaction, precipitated on the electrode, and
colored.
CITATION LIST
Patent Literature
[0010] PTL 1 Japanese Patent Laid-Open No. 56-67881 [0011] PTL 2
Japanese Patent Laid-Open No. 51-146253
Non Patent Literature
[0011] [0012] NPL 1 Advanced Functional Materials, 16, 426
(2006)
[0013] In PTL 1, the delocalization of unstable radical cations in
its molecule enhances stability. However, the stability is not
sufficient. In the case where the redox reaction is repeated, the
material is degraded, thereby disadvantageously reducing the
performance of the EC device.
[0014] Furthermore, the conductive polymer absorbs visible light in
the electrically neutral state. That is, the polymer is colored in
the electrically neutral state. Thus, if there is a portion where
the electrochemical reaction occurs insufficiently, the portion is
maintained to be a colored state, thus causing difficulty in
achieving high transparency.
[0015] In the viologen-based organic EC compound described in PTL
2, the repetition of the precipitation and dissolution causes
degradation phenomena.
[0016] The degradation phenomena can be attributed to irreversible
crystallization and insolubilization due to polymerization. The
degradation leads to a "residual portion" in which the portion is
not transparent even in a state in which the portion should be
bleached.
[0017] Furthermore, the viologen-based organic EC compound forms
unstable radical cations at the time of reduction. Unfortunately,
the molecule does not have a mechanism for stabilizing the radical
cations, so that the stability of the radical cations is low.
Hence, the device has low durability.
[0018] Accordingly, it is an object of the present invention to
provide an EC device having high durability, a high response speed,
and high transparency when the device is bleached.
SUMMARY OF INVENTION
[0019] The present invention provides an electrochromic device
including a pair of electrodes and a composition arranged between
the pair of electrodes, the composition containing an electrolyte
and an organic electrochromic compound, in which the organic
electrochromic compound includes an electrochromic portion that
exhibits electrochromic properties and an aromatic ring directly
bonded to the electrochromic portion, the electrochromic portion
forms one conjugated plane, an atom of the aromatic ring and
adjacent to an atom bonded to the electrochromic portion has a
substituent having a volume equal to or larger than the volume of a
methyl group, and the pair of electrodes has an interelectrode
distance of 150 .mu.m or less.
[0020] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a schematic cross-sectional view of an EC device
according to an embodiment of the present invention.
[0022] FIG. 2 is a graph illustrating durable stability against
redox cycles in Example 2.
[0023] FIG. 3 is a graph illustrating durable stability against
redox cycles in Example 3.
[0024] FIG. 4 is a graph illustrating the response time of an EC
device in Example 10.
DESCRIPTION OF EMBODIMENTS
[0025] An EC device according to the present invention includes a
pair of electrodes and a composition arranged between the pair of
electrodes, the composition containing an electrolyte and an
organic electrochromic compound, in which the organic
electrochromic compound includes an electrochromic portion that
exhibits electrochromic properties and an aromatic ring directly
bonded to the electrochromic portion, the electrochromic portion
forms one conjugated plane, an atom of the aromatic ring and
adjacent to an atom bonded to the electrochromic portion has a
substituent having a volume equal to or larger than the volume of a
methyl group, and the pair of electrodes has an interelectrode
distance of 150 .mu.m or less.
[0026] An EC device according to the present invention will be
described below with reference to the drawings. FIG. 1 is a
schematic cross-sectional view of an EC device according to an
embodiment of the present invention.
[0027] The EC device illustrated in FIG. 1 includes a pair of
transparent electrodes 11 and a composition 12 arranged between the
pair of transparent electrodes, the composition 12 containing an
electrolyte and an organic EC compound. The pair of the electrodes
has a constant interelectrode distance defined by spacers 13.
[0028] In the EC device, the pair of the electrodes is arranged
between a pair of transparent substrates 10.
[0029] The term "transparent" used here indicates that the light
transmittance is 10% to 100% in the visible region. However, the EC
device is merely an exemplary EC device according to the present
invention. The EC device according to the present invention is not
limited thereto.
[0030] For example, an antireflection coating film may be arranged
between one of the transparent substrates 10 and a corresponding
one of the transparent electrodes 11 and between one of the
transparent electrodes 11 and the organic EC medium 12. The EC
composition is a composition containing an organic EC compound. The
EC composition is also merely referred to as a "liquid" or
"composition".
[0031] The composition 12 contained in the EC device according to
the present invention will now be described. The composition 12 is
one in which the organic EC compound and a supporting electrolyte
are dissolved in a solvent.
[0032] The organic EC compound according to this embodiment has an
electrochromic portion and an aromatic ring-containing peripheral
portion. The electrochromic portion is a portion that provides
electrochromic properties. The peripheral portion has a substituent
that protects the electrochromic portion.
[0033] In this embodiment, the aromatic ring in the organic EC
compound and the substituent on the aromatic ring are collectively
referred to as the "peripheral portion".
[0034] The peripheral portion is bonded to the electrochromic
portion where a redox reaction occurs. Preferably, the peripheral
portion does not inhibit the redox reaction. Thus, the peripheral
portion preferably has a high redox potential.
[0035] The peripheral portion protects the electrochromic portion.
Thus, the compound has high stability against oxidation.
[0036] The EC device according to the present invention includes
the compound having high stability against oxidation and thus has
high durability.
[0037] The substituent of the peripheral portion inhibits the
approach of another molecule to the electrochromic portion by the
effect of steric hindrance, and so is also referred to as a
"sterically hindered group" because of its function.
[0038] The electrochromic portion which exhibits electrochromic
properties and which has one conjugated plane has a structure
including one or more heteroaromatic rings, such as thiophene,
pyrrole, furan, pyridine, thiazole, and imidazole, or aromatic
hydrocarbon rings, such as a benzene ring, these rings having
.pi.-electron conjugated systems.
[0039] Here, .pi. electrons on one heteroaromatic ring or one
aromatic ring are delocalized and distributed over the ring. Thus,
one ring may be regarded as forming one conjugated plane.
[0040] Furthermore, also in a structure in which two or more
heteroaromatic rings or aromatic rings are linked together, .pi.
electrons are delocalized on these rings. Thus, the rings may be
regarded as forming one conjugated plane.
[0041] In the case where two or more heteroaromatic rings are
linked together, higher coplanarity of the rings is preferred. This
is because higher coplanarity results in the extension of molecular
conjugation and longer molecular conjugation results in higher
stability of the molecule.
[0042] However, in the EC device according to the present
invention, when the organic EC compound is bleached, preferably,
the organic EC compound does not absorb light in the visible
region. Thus, preferably, the conjugated structure of the aromatic
ring in the electrochromic portion is not excessively long.
[0043] The reason for this is that a long conjugates structure
results in a narrow gap between the highest occupied molecular
orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO),
thereby absorbing light in the visible region, which has low
energy.
[0044] Note that each of the heteroaromatic ring and the aromatic
hydrocarbon ring may have a substituent.
[0045] Examples of the substituent include an alkyl group, an aryl
group, a heterocyclic group, an alkyl ether group, an alkoxy group,
and an aralkyl group. In particular, examples of the substituent
include an alkyl group having 1 to 10 carbon atoms, an alkoxy group
having 1 to 10 carbon atoms, and a phenyl group.
[0046] The EC device according to the present invention contains a
cathodically electrochromic organic compound. The cathodically
electrochromic organic compound is an electrochromic compound that
is colored when reduced.
[0047] In an EC device containing both the cathodically
electrochromic organic compound and an anodically electrochromic
organic compound, an electrochromic reaction occurs at each of a
pair of electrodes, thus resulting in a rapid change in
transmittance. That is, the EC device is one having a high speed of
response.
[0048] Furthermore, the EC device according to the present
invention may contain another compound.
[0049] While specific structural formulae of the electrochromic
portion will be exemplified below, the electrochromic portion
according to this embodiment is not limited thereto.
##STR00001## ##STR00002## ##STR00003##
[0050] The electrochromic portion has a conjugated structure and
thus has the effect of increasing the stability of radical cations
formed in the molecule. A longer conjugated structure in the
molecule enhances the effect. However, in order to provide a
bleached state when the compound is in an electrically neutral
state, preferably, the conjugated structure is not excessively
long.
[0051] To increase the stability of radical cations, the
possibility that the radical cations come into contact with other
molecules may be reduced. For example, the presence of the
peripheral portion included in the organic EC compound according to
this embodiment may reduce the possibility that the radical cations
come into contact with other molecules.
[0052] That is, the organic EC compound according to this
embodiment includes the peripheral portion, so that the stability
of radical cations is high even in the case of a molecule having a
short conjugated structure.
[0053] It is conceivable that the instability of radical cations is
attributed to the recombination of radicals and the abstraction of
hydrogen from other molecules by radicals on the basis of the high
reactivity of radicals.
[0054] That is, the reaction is caused by the contact of radicals
with other molecules. It is thus conceivable that the suppression
of the possibility of the contact with other molecules is highly
effective.
[0055] Hence, the steric hindrance of a substituent on the aromatic
ring and on an atom adjacent to an atom directly bonded to the
electrochromic portion stabilizes radical cations. This is because
the steric hindrance of the substituent inhibits the contact of
radical cations with other molecules.
[0056] Examples of the aromatic ring contained in the peripheral
portion include nitrogen atom-containing heteroaromatic rings, such
as a pyridine ring and a pyrazine ring, in addition to a benzene
ring and a naphthyl ring. Among them, an aromatic ring consisting
of carbon atoms is preferred.
[0057] The substituent on the aromatic ring serves to allow the
conjugated plane of the electrochromic portion to be orthogonalized
to the plane of the peripheral portion and serves to protect the
electrochromic portion where radical cations are formed on the
basis of the effect of steric hindrance. From this point of view, a
substituent having a volume equal to or larger than the volume of a
methyl group is preferred.
[0058] This is because the peripheral portion having a substituent
with a volume equal to or larger than the volume of a methyl group
has a large excluded volume.
[0059] The term "excluded volume" used in this embodiment indicates
the volume of a body of revolution defined by a locus formed by
revolving the peripheral portion. In the body of revolution defined
by a locus obtained by revolving the peripheral portion, a single
bond that links the peripheral portion with the electrochromic
portion serves as the axis of revolution.
[0060] Examples of the substituent having a volume equal to or
larger than the volume of a methyl group according to this
embodiment include alkyl groups, such as methyl, ethyl, isopropyl,
tert-butyl, dodecyl, and cyclohexyl groups; aryl groups, such as
phenyl and biphenyl groups, which may have a substituent; alkoxy
groups, such as methoxy, isopropoxy, n-butoxy, and tert-butoxy
groups; and alkyl ester groups, such as methyl ester, isopropyl
ester, and tert-butyl ester groups.
[0061] As the substituent in the peripheral portion according to
this embodiment, an electron-donating group, for example, an amino
group or a diphenylamino group, having strong electron-donating
properties may be used in addition to a substituent consisting of
carbon, oxygen, and hydrogen.
[0062] Furthermore, an electron-withdrawing group, such as a
halogen-containing group, e.g., a trifluoromethyl group, and a
nitrile group, may be used. In particular, when the electrochromic
portion is electron rich, an electron-withdrawing peripheral
portion is effective.
[0063] Among them, in particular, electron-donating groups, such as
alkyl groups and alkoxy groups, are preferred. Alkyl groups and
alkoxy groups each having 1 to 10 carbon atoms may be preferably
used.
[0064] In the case where an electron-donating group is contained,
the electrochromic portion has a high electron density and thus has
a low oxidation potential, thereby providing a device having a low
driving voltage.
[0065] The peripheral portion according to this embodiment is a
portion to which molecular conjugation in the electrochromic
portion does not extend. The boundary between the electrochromic
portion and the peripheral portion is determined by whether
molecular conjugation is present or not.
[0066] In an actual molecule, however, fluctuations due to thermal
motion and quantum-chemical fluctuations exist; hence, the
molecular orbital is not completely disrupted. In this embodiment,
in the case of small resonance, molecular conjugation is regarded
as not being present.
[0067] A smaller resonance between the electrochromic portion and
the peripheral portion is preferred. Thus, .pi.-electron orbitals
of the electrochromic portion and the peripheral portion preferably
intersect at an angle close to 90.degree.. In the case where the
.pi.-electron orbitals of the peripheral portion and the
electrochromic portion are orthogonalized, the resonance is
extremely small.
[0068] Preferably, two atoms adjacent to an atom having a bond that
links the electrochromic portion and the peripheral portion each
have a substituent having a volume equal to or larger than the
volume of a methyl group in order that the angle between the
electrochromic portion and the peripheral portion may be close to
90.degree..
[0069] Furthermore, preferably, the oxidation potential of the
peripheral portion is relatively higher than that of the
electrochromic portion. That is, an organic EC compound having the
peripheral portion that is less likely to be oxidized is more
preferred. The fact that the redox potential is high is that the
HOMO lies deep.
[0070] The dihedral angle formed by the electrochromic portion and
the peripheral portion according to this embodiment is preferably
close to 90.degree.. The reason for this is that because a molecule
having a conjugated structure has high planarity, a reaction with
another molecule occurs in the direction perpendicular to the
conjugated plane.
[0071] The following table illustrates, as an example, a value of
the dihedral angle between a dithienothiophene ring and a phenyl
ring determined by molecular orbital calculation. The
dithienothiophene ring is illustrated as exemplified structure W-17
described above. Note that dithienothiophene corresponds to the
electrochromic portion and that a phenyl group substituted with
hydrogen or a methyl group corresponds to the peripheral
portion.
[0072] The dihedral angle in a ground state was determined by
structural optimization calculations using Gaussian 03* Revision D.
01. The density functional theory was used as a quantum chemical
calculation method using the B3LYP functional.
[0073] In Gaussian 03, Revision D. 01, the 6-31G* basis function
was used.
*Gaussian 03, Revision D. 01, M. J. Frisch, G. W. Trucks, H. B.
Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A.
Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M.
Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi,
G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M.
Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima,
Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C.
Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P.
Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D.
Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.
Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A.
Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W.
Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and J. A.
Pople, Gaussian, Inc., Wallingford Conn., 2004.
TABLE-US-00001 TABLE 1 Compound ##STR00004## ##STR00005## Dihedral
angle 28.degree. 90.degree. between two rings
[0074] As illustrated above, in the case where each of the atoms of
the peripheral portion and adjacent to the atom bonded to the
electrochromic portion has a substituent, the conjugated plane of
the electrochromic portion intersects with the plane of the
peripheral portion at an angle close to 90.degree., which is
preferred.
[0075] It is well known that the oxidation potential of a molecular
species correlates with the HOMO. A higher HOMO results in a lower
oxidation potential. That is, in the organic EC compound according
to this embodiment, the HOMO of the electrochromic portion lies
preferably higher than the HOMO of the peripheral portion.
[0076] The fact that the HOMO of the electrochromic portion lies
higher than the HOMO of the peripheral portion indicates that the
electrochromic portion is likely to be oxidized compared with the
peripheral portion.
[0077] Here, the fact that the HOMO lies high indicates that it
lies closer to the vacuum level. Thus, the HOMO may also be
expressed as the shallow HOMO.
[0078] Table 2 illustrates examples of a combination in which the
electrochromic portion is more easily oxidized than the peripheral
portion and illustrates molecular orbital calculation results of a
single molecular structure that includes dithienothiophene serving
as the electrochromic portion and a corresponding one of aromatic
rings substituted with various substituents, each aromatic ring
serving as the peripheral portion.
[0079] The molecular orbital calculations were conducted using the
foregoing electronic state calculation software, Gaussian 03*
Revision D. 01.
[0080] The calculated values from the molecular orbital
calculations of the electrochromic portion were obtained on the
assumption that the electrochromic portion is present in the form
of an independent compound. The calculated values from the
molecular orbital calculations of the peripheral portion were also
obtained on the assumption that the peripheral portion is present
not in the form of a substituent but in the form of an independent
compound.
[0081] In the organic EC compound according to this embodiment, the
molecular conjugation is broken between the electrochromic portion
and the peripheral portion. Thus, characteristics of the entire
molecule may be discussed by the foregoing calculation method.
[0082] In the case where dithienothiophene is used as the
electrochromic portion and where the structures illustrated in the
table are each used as the peripheral portion, the electrochromic
portion has a higher HOMO energy than those of the peripheral
portions. This structure is one in which the electrochromic portion
is more likely to be oxidized.
TABLE-US-00002 TABLE 2 eV eV HOMO LUMO Peripheral
4,4'-Di-tert-butyl-1,1-biphenyl group -5.74 -0.48 portion
(peripheral portion of exemplified compound A-10) Terphenyl group
-5.97 -0.74 (peripheral portion of exemplified compound A-7)
Trimethylphenyl group -6.20 -0.36 (peripheral portion of
exemplified compound A-1) 2-Isopropoxy-6-methoxyphenyl group -5.67
-0.36 (peripheral portion of exemplified compound A-11)
Electrochromic Dithienothiophene -5.63 -0.93 portion
[0083] While examples of the specific structural formula of the
organic EC compound including the electrochromic portion and the
peripheral portion according to this embodiment will be illustrated
below, the organic EC compound according to the present invention
is not limited thereto.
##STR00006## ##STR00007## ##STR00008## ##STR00009## ##STR00010##
##STR00011## ##STR00012## ##STR00013## ##STR00014##
##STR00015##
[0084] Among these exemplified compounds, the compounds illustrated
in group A are examples of a compound including dithienothiophene
serving as the electrochromic portion. The compounds illustrated in
group B are examples of a compound in which the substituent on the
peripheral portion is a methoxy group or an isopropoxy group.
[0085] Each of the compounds illustrated in group A and group B has
a structure in which the peripheral portion protects the
electrochromic portion that exhibits electrochromic properties.
[0086] Thus, EC devices containing these compounds serving as EC
materials have high durability against the repetition of a redox
reaction.
[0087] The organic EC compound according to this embodiment may be
synthesized from a combination of a halide of a compound to be
formed into the electrochromic portion and a boronic acid or
boronate of a compound to be formed into the peripheral portion or
from a combination of a boronic acid or boronate of a compound to
be formed into the electrochromic portion and a halide of a
compound to be formed into the peripheral portion, by a coupling
reaction in the presence of a Pd catalyst.
[0088] An example of a synthesis method for the case where the
electrochromic portion is composed of dithienothiophene is
illustrated in formula [3]. In the formula, X represents a halogen
atom; and A and A' each represent a substituent on the peripheral
portion. The dithienothiophene moiety in the formula may be
replaced with other organic EC compounds to synthesize the organic
EC compounds according to this embodiment.
##STR00016##
[0089] In the external electrode according to this embodiment, the
organic EC compound according to this embodiment may be used alone,
together with another organic EC compound according to this
embodiment, or together with another known organic EC compound.
[0090] A first aspect of the EC device according to this embodiment
is an EC device including a liquid in which an anodically EC
organic compound alone is dissolved in a solvent, the anodically EC
organic compound being colored by oxidation. A second aspect
thereof is an EC device including a liquid in which an anodically
EC organic compound and a cathodically EC organic compound, such as
viologen, are both dissolved in a solvent, the cathodically EC
organic compound being colored by reduction.
[0091] The device having the structure according to the first
aspect is referred to as a "unipolar-type device". The device
having the structure according to the second aspect is referred to
as a "bipolar-type device".
[0092] In the case where the bipolar-type device is driven, radical
cations are formed by an oxidation reaction on one electrode, and
radical cations are formed by reduction on the other electrode.
[0093] The radical cations and the radical cations diffuse in the
solution and collide with each other to cause a redox reaction.
That is, the redox reaction occurs in portions other than the
electrodes. Thus, the radical cations and the radical cations
disappear. In other words, they are formed into substances before
the redox reaction, thereby causing bleaching.
[0094] The rate of a coloring reaction needs to be higher than that
of the bleaching reaction. Thus, the redox reaction on the
electrodes needs to be performed at a higher rate than that of the
reaction in the liquid.
[0095] For this reason, a large current is required, so that the
power consumption is higher than that of the unipolar-type device.
From this point of view, the unipolar-type EC device according to
the first aspect is preferred.
[0096] Next, members constituting the EC device according to this
embodiment will be described. First, the electrolyte and the
solvent contained in the liquid in the EC device will be described
together with the organic EC compound.
[0097] The electrolyte is not limited as long as it is an ionically
dissociable salt, has satisfactory solubility in a solvent, and
high compatibility if it is a solid electrolyte. In particular, the
electrolyte preferably has electron-donating properties.
[0098] Examples of a supporting electrolyte include inorganic ionic
salts, such as various alkali metal salts and alkaline-earth metal
salts; quaternary ammonium salts; and cyclic quaternary ammonium
salts.
[0099] Specific examples thereof include salts of alkali metals of
Li, Na, and K, such as LiClO.sub.4, LiSCN, LiBF.sub.4, LiAsF.sub.6,
LiCF.sub.3SO.sub.3, LiPF.sub.6, LiI, NaI, NaSCN, NaClO.sub.4,
NaBF.sub.4, NaAsF.sub.6, KSCN, and KCl; and quaternary ammonium
salts and cyclic quaternary ammonium salts, such as
(CH.sub.3).sub.4NBF.sub.4, (C.sub.2H.sub.5).sub.4NBF.sub.4,
(n-C.sub.4H.sub.9).sub.4NBF.sub.4, (C.sub.2H.sub.5).sub.4NBr,
(C.sub.2H.sub.5).sub.4NClO.sub.4, and
(n-C.sub.4Hg).sub.4NClO.sub.4.
[0100] The solvent that dissolves the organic EC compound and the
supporting electrolyte is not particularly limited as long as it
can dissolve the organic EC compound and the supporting
electrolyte. In particular, the solvent preferably has
polarity.
[0101] Specific examples thereof include polar organic solvents,
such as methanol, ethanol, propylene carbonate, ethylene carbonate,
dimethyl sulfoxide, dimethoxyethane, .gamma.-butyrolactone,
.gamma.-valerolactone, sulfolane, dimethylformamide,
dimethoxyethane, tetrahydrofuran, acetonitrile, propionitrile,
benzonitrile, dimethylacetamide, methylpyrrolidinone, and
dioxolane.
[0102] Furthermore, a highly viscous or gel-like composition
prepared by further incorporating a polymer or a gelling agent into
the EC medium may be used.
[0103] The polymer is not particularly limited. Examples thereof
include polyacrylonitrile, carboxymethyl cellulose, polyvinyl
chloride, polyethylene oxide, polypropylene oxide, polyurethane,
polyacrylate, polymethacrylate, polyamide, polyacrylamide,
polyester, and Nafion (registered trademark).
[0104] Next, the transparent substrates and the transparent
electrodes will be described. As the transparent substrates 10, for
example, colorless or colored glass, tempered glass, or a colorless
or colored transparent resin may be used.
[0105] Specific examples thereof include polyethylene
terephthalate, polyethylene naphthalate, polynorbornene, polyamide,
polysulfone, polyether sulfone, polyether ether ketone,
polyphenylene sulfide, polycarbonate, polyimide, and polymethyl
methacrylate.
[0106] Examples of the electrode material 11 include metals and
metal oxides, such as indium tin oxide alloys (ITO), fluorine-doped
tin oxide (FTC)), tin oxide (NESA), indium zinc oxide (IZO), silver
oxide, vanadium oxide, molybdenum oxide, gold, silver, platinum,
copper, indium, and chromium; silicon materials, such as
polycrystalline silicon and amorphous silicon; and carbon
materials, such as carbon black, graphite, glassy carbon.
[0107] Furthermore, conductive polymers having improved
conductivity by doping treatment and so forth (e.g., polyaniline,
polypyrrole, polythiophene, polyacetylene, polyparaphenylene, and
complexes of polyethylenedioxythiophene (PEDOT) and polystyrene
sulfonic acid) may be preferably used.
[0108] In an optical filter according to this embodiment, the
optical filter requires transparency. Thus, ITO, FTO, IZO, NESA,
conductivity-improved conductive polymers, which do not absorb
light in the visible region, are particularly preferably used. A
known method for improving conductivity may be employed.
[0109] They may be used in various forms, such as bulk and
fine-particle forms. These electrode materials may be used alone.
Alternatively, the plural electrode materials may be used in
combination.
[0110] The spacers 13 are arranged between the pair of electrodes
11 to give a space to accommodate the composition 12 containing the
organic EC compound. Specifically, polyimide, Teflon, fluorocarbon
rubber, epoxy resins, and so forth may be used. The spacers are
able to maintain the interelectrode distance of the EC device.
[0111] The EC device according to this embodiment may include an
inlet for liquid, the inlet being formed by the pair of electrodes
and the spacers. After the composition containing the organic EC
compound is fed from the inlet, the inlet is covered with a sealing
member. Then the inlet is hermetically sealed with an adhesive or
the like, thereby providing a device.
[0112] The sealing member also serves to ensure isolation such that
the adhesive does not come into contact with the organic EC
compound. While the shape of the sealing member is not particularly
limited, a tapered shape, such as a wedge shape, is preferred.
[0113] The EC device according to this embodiment preferably has an
interelectrode distance of 150 .mu.m or less. The reason for this
is that because the peripheral portion of the organic EC compound
according to this embodiment has a large excluded volume, the
diffusion velocity in the solution is low.
[0114] In the device having a low diffusion velocity of the organic
EC compound, it takes a long time from the time of the application
of a voltage to the device until the transmittance of the device
reaches a target transmittance. That is, the device is one having a
low response speed. For the compound having low diffusion velocity,
a reduction in diffusion length increases the response speed. In
the EC device, a reduction in interelectrode distance results in a
reduction in diffusion length.
[0115] The EC device according to this embodiment has
characteristics in which the bleaching response speed is sharply
changed at an interelectrode distance of about 150 .mu.m, as
described in Example 10.
[0116] The response speed of the EC device is preferably 10 seconds
or less. The response speed of the EC device according to this
embodiment is 10 seconds or less when the interelectrode distance
is 150 .mu.m or less.
[0117] The EC device according to this embodiment having an
interelectrode distance of 150 .mu.m or less has a high response
speed.
[0118] The lower limit of the interelectrode distance is 100 nm in
order to inhibit the electrical continuity between the electrodes.
That is, the interelectrode distance of the EC device according to
this embodiment is preferably in the range of 100 nm to 150
.mu.m.
[0119] The term "response time" used in this embodiment indicates
the length of time from a state having the initial transmittance
until the state is changed to a state having a transmittance of
95%.
[0120] A method for forming the EC device according to this
embodiment is not particularly limited. A method may be employed in
which an organic EC compound-containing liquid prepared in advance
is injected into a gap between the pair of electrode substrates by,
for example, a vacuum injection method, an atmospheric injection
method, or a meniscus method.
[0121] The EC device according to this embodiment may be used for
optical filters, lens units, and image pickup apparatuses.
[0122] The EC device according to this embodiment has high
durability, high transmittance in a bleached state, and a high
coloring-bleaching response speed and thus may be preferably used
to control the quantity of light incident on an image pickup device
in a camera or the like and to control the properties of the
incident wavelength distribution. The control of the incident
wavelength distribution is effective in converting the color
temperature.
[0123] That is, the arrangement of the EC device in an optical path
of an image pickup optical system communicating with the image
pickup device enables us to control the quantity of light incident
on the image pickup device or the properties of the incident
wavelength distribution. The image pickup optical system may also
be referred to as a lens system. Examples of the image pickup
optical system include lens units each including a plurality of
lenses.
[0124] The EC device according to this embodiment functions as an
optical filter when connected to a transistor. Examples of the
transistor include TFT and MIM devices.
[0125] An image pickup apparatus according to this embodiment
includes an image pickup device and an image pickup optical system
including an optical filter. The EC device included in the image
pickup apparatus may be located at any position, e.g., a position
in front of the image pickup optical system or a position right in
front of the image pickup device.
[0126] The EC device provides high transmittance in a bleached
state. Thus, a sufficient quantity of light transmitted is provided
with respect to incident light. Furthermore, in a colored state,
optical properties in which incident light is surely shielded or
modulated are provided. Moreover, the EC device has excellent redox
cycle properties and thus has a long lifetime.
EXAMPLES
[0127] Examples of a method for synthesizing an organic EC compound
according to this embodiment will be described below. Target
organic EC compounds may be synthesized by appropriately changing
electrochromic portions and peripheral portions in synthesis
examples.
Synthesis Example 1
Synthesis of Exemplified Compound A-1
##STR00017##
[0129] In a 50-mL reaction vessel, XX-1
(2,6-dibromodithieno[3,2-b:2',3'-d]thiophene) (732 mg, 2.06 mmol)
and 2,4,6-trimethylphenylboronic acid (994 mg, 6.06 mmol) were
dissolved in toluene (6 ml). Dissolved oxygen was removed by
nitrogen.
[0130] Next, Pd(OAc).sub.2 (7.1 mg, 0.0316 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (32.4 mg,
0.0792 mmol), and tripotassium phosphate (1.68 g, 7.92 mmol) were
added thereto in a nitrogen atmosphere. The mixture was heated and
refluxed at 130.degree. C. to perform a reaction for 12 hours.
[0131] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane) to give a white solid power A-1 (510 mg, yield:
57%). Measurement by matrix-assisted laser desorption
ionization-mass spectrometry (MALDl-MS) demonstrated that M+ of
this compound was found to be 433.
Synthesis Example 2
Synthesis of Exemplified Compound A-7
##STR00018##
[0133] In a 50-ml reaction vessel, XX-2 (526.2 mg, 1.17 mmol) and
XX-3 (1071.2 mg, 3.0 mmol) were mixed in a toluene/ethyl
alcohol/tetrahydrofuran (6 ml/3 ml/8 ml) mixed solvent. Dissolved
oxygen was removed by nitrogen.
[0134] Note that XX-3 is a compound synthesized according to The
Journal of Organic Chemistry, 51, 3162 (1986).
[0135] Next, Pd(PPh.sub.3).sub.4 (14.0 mg, 0.01215 mmol) and an
aqueous solution (1.5 ml) of 2 M cesium carbonate were added
thereto in a nitrogen atmosphere. The mixture was then heated at
85.degree. C. to perform a reaction for 12 hours.
[0136] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=3/2) to give a white solid power A-7 (72
mg, yield: 9.4%). Measurement by MALDl-MS demonstrated that M+ of
this compound was found to be 652.
[0137] The longest absorption wavelength of XX-3 to be formed into
the structure of the peripheral portion was 307 nm. The longest
absorption wavelength of dithienothiophene to be formed into the
structure of the electrochromic portion was 335 nm. That is, the
longest absorption wavelength of the electrochromic portion was
longer than that of the peripheral portion.
Synthesis Example 3
Synthesis of Exemplified Compound A-10
##STR00019##
[0139] In a 50-ml reaction vessel, XX-1 (177.05 mg, 0.50 mmol) and
XX-4 (588.6 mg, 1.50 mmol) were mixed in a toluene/ethyl alcohol (6
ml/2 ml) mixed solvent. Dissolved oxygen was removed by
nitrogen.
[0140] Note that XX-4 is a compound synthesized according to
WO2005/054212. Next, Pd(PPh3)4 (57.8 mg, 0.05 mmol) and an aqueous
solution (1.0 ml) of 2 M cesium carbonate were added thereto in a
nitrogen atmosphere. The mixture was then heated at 85.degree. C.
to perform a reaction for 17 hours.
[0141] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/toluene=5/1) to give a white solid power A-10 (125
mg, yield: 29%). Measurement by MALDl-MS demonstrated that M+ of
this compound was found to be 724.
Synthesis Example 4
Synthesis of Exemplified Compound A-12
##STR00020##
[0143] In a 50-ml reaction vessel, XX-1 (177.05 mg, 0.50 mmol) and
2-isopropoxy-6-methoxyphenylboronic acid (420 mg, 2.0 mmol) were
mixed in a toluene/tetrahydrofuran (6 ml/3 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen.
[0144] Next, Pd(OAc).sub.2 (2.3 mg, 0.01 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (10.3 mg,
0.025 mmol), and tripotassium phosphate (575.7 mg, 2.5 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
at 110.degree. C. to perform a reaction for 8 hours.
[0145] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/2) to give a white solid power A-12 (187
mg, yield: 71%). Measurement by MALDl-MS demonstrated that M+ of
this compound was found to be 524.
Synthesis Example 5
Synthesis of Exemplified Compound B-1
##STR00021##
[0147] In a 50-ml reaction vessel, XX-5 (2,5-dibromothiophene)
(241.9 mg, 1.0 mmol) and 2-isopropoxy-6-methoxyphenylboronic acid
(753.1 mg, 3.5 mmol) were mixed in a toluene/tetrahydrofuran (4
ml/4 ml) mixed solvent. Dissolved oxygen was removed by
nitrogen.
[0148] Next, Pd(OAc).sub.2 (4.5 mg, 0.02 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (20.53 mg,
0.05 mmol), and tripotassium phosphate (1162.4 mg, 5.05 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
at 110.degree. C. to perform a reaction for 8 hours.
[0149] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/4) to give a white solid power B-1
(362.8 mg, yield: 86.3%). Measurement by MALDl-MS demonstrated that
M+ of this compound was found to be 412.2.
Synthesis Example 6
Synthesis of Exemplified Compound B-6
##STR00022##
[0151] In a 50-ml reaction vessel, XX-6
(2,5-dibromoethylenedioxythiophene) (500 mg, 1.67 mmol) and
2-isopropoxy-6-methoxyphenylboronic acid (1.05 g, 5.0 mmol) were
mixed in a toluene/tetrahydrofuran (10 ml/5 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen.
[0152] Next, Pd(OAc).sub.2 (19 mg, 0.083 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (89 mg,
0.22 mmol), and tripotassium phosphate (1.92 g, 8.35 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 7
hours.
[0153] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/ethyl acetate=4/3) to give a white solid power B-6
(420 mg, yield: 54%). Measurement by MALDl-MS demonstrated that M+
of this compound was found to be 470.
Synthesis Example 7
Synthesis of Exemplified Compound B-7
##STR00023##
[0155] In a 50-ml reaction vessel, XX-7 (2,5-dibromobithiophene)
(326.3 mg, 1.01 mmol) and 2-isopropoxy-6-methoxyphenylboronic acid
(749.8 mg, 3.57 mmol) were mixed in a toluene/tetrahydrofuran (4
ml/4 ml) mixed solvent. Dissolved oxygen was removed by
nitrogen.
[0156] Next, Pd(OAc).sub.2 (5.9 mg, 0.026 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (21.4 mg,
0.052 mmol), and tripotassium phosphate (1123.7 mg, 4.88 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 8
hours.
[0157] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/3) to give a white solid power B-7
(418.8 mg, yield: 84.1%). Measurement by MALDl-MS demonstrated that
M+ of this compound was found to be 494.2.
Synthesis Example 8
Synthesis of Exemplified Compound B-10
##STR00024##
[0159] In a 50-ml reaction vessel, XX-8 (440.1 mg, 1 mmol) and
2-isopropoxy-6-methoxyphenylboronic acid (751.1 mg, 3.58 mmol) were
mixed in a toluene/tetrahydrofuran (4 ml/4 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen.
[0160] Next, Pd(OAc).sub.2 (5.1 mg, 0.023 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (22.8 mg,
0.056 mmol), and tripotassium phosphate (1193.1 mg, 5.18 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 8
hours.
[0161] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/ethyl acetate=4/3) to give a white solid power B-10
(177.3 mg, yield: 29.03%). Measurement by MALDl-MS demonstrated
that M+ of this compound was found to be 610.2.
Synthesis Example 9
Synthesis of Exemplified Compound B-11
##STR00025##
[0163] In a 50-ml reaction vessel, XX-9 (200 mg, 0.671 mmol) and
2-isopropoxy-6-methoxyphenylboronic acid (563 mg, 2.684 mmol) were
mixed in a toluene/tetrahydrofuran (6 ml/3 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen.
[0164] Next, Pd(OAc).sub.2 (3.0 mg, 0.013 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (13.8 mg,
0.034 mmol), and tripotassium phosphate (772 mg, 3.36 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 8
hours.
[0165] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/2) to give a white solid power B-11 (235
mg, yield: 75%). Measurement by MALDl-MS demonstrated that M+ of
this compound was found to be 468.
Synthesis Example 10
Synthesis of Exemplified Compound B-16
##STR00026##
[0167] (1) In a 300-mL reaction vessel, XX-10 (1.25 g, 3.53 mmol)
and phenylboronic acid (1.29 g, 10.59 mmol) were dissolved in
toluene (70 ml). Dissolved oxygen was removed by nitrogen.
[0168] Next, Pd(OAc).sub.2 (15.9 mg, 0.0706 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (72.5 mg,
0.1765 mmol), and tripotassium phosphate (3.75 g, 17.65 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 140.degree. C. to perform a reaction for 13
hours.
[0169] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/ethyl acetate) to give a white solid power XX-11
(1.23 g, yield: 100%).
[0170] (2) In a 300-mL reaction vessel, XX-11 (1.13 g, 3.242 mmol)
obtained in item (1) was dissolved in N,N-dimethylformamide (DMF)
(65 ml). Then N-bromosuccinimide (1.44 g, 8.106 mmol) was added
thereto. The mixture was stirred at 70.degree. C. for 24 hours. The
reaction solution was cooled to room temperature. Then the reaction
solution was subjected to extraction with chloroform, washing with
water, and concentration under reduced pressure to give a pale
yellow power XX-12 (1.55 g, yield: 94%).
[0171] (3) In a 50-ml reaction vessel, XX-12 (200 mg, 0.395 mmol)
and 2-isopropoxy-6-methoxyphenylboronic acid (332 mg, 1.580 mmol)
were mixed in a toluene/tetrahydrofuran (3 ml/3 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen. Next, Pd(OAc).sub.2 (1.8
mg, 0.0079 mmol), 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl
(S-Phos) (8.13 mg, 0.0198 mmol), and tripotassium phosphate (455
mg, 1.98 mmol) were added thereto in a nitrogen atmosphere. The
mixture was then heated and refluxed to perform a reaction for 8
hours.
[0172] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/2) to give a white solid power B-16 (225
mg, yield: 84%). Measurement by MALDl-MS demonstrated that M.sup.+
of this compound was found to be 676.
Synthesis Example 11
Synthesis of Exemplified Compound B-18
##STR00027##
[0174] (1) In a 50-ml reaction vessel, XX-5 (300 mg, 1.24 mmol) and
XX-13 (1.10 g, 3.72 mmol) were mixed in a toluene/tetrahydrofuran
(8 ml/4 ml) mixed solvent. Dissolved oxygen was removed by
nitrogen.
[0175] Next, Pd(OAc).sub.2 (8.4 mg, 0.037 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (40.7 mg,
0.0992 mmol), and tripotassium phosphate (1.43 g, 6.2 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 7
hours.
[0176] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane) to give a colorless viscous liquid XX-14 (360 mg,
yield: 70%).
[0177] (2) In a 100-mL reaction vessel, XX-14 (355 mg, 0.852 mmol)
obtained in item (1) was dissolved in N,N-dimethylformamide (DMF)
(25 ml).
[0178] Then N-bromosuccinimide (333 mg, 1.87 mmol) was added
thereto. The mixture was stirred at room temperature for 8 hours.
Water was added to the reaction solution. Then the reaction
solution was subjected to extraction with chloroform, washing with
water, and concentration under reduced pressure to give XX-15 (470
mg, yield: 96%).
[0179] (3) In a 50-ml reaction vessel, XX-15 (470 mg, 0.818 mmol)
and 2-isopropoxy-6-methoxyphenylboronic acid (515 mg, 2.45 mmol)
were mixed in a toluene/tetrahydrofuran (5 ml/2.5 ml) mixed
solvent. Dissolved oxygen was removed by nitrogen.
[0180] Next, Pd(OAc).sub.2 (5.5 mg, 0.0245 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (27 mg,
0.065 mmol), and tripotassium phosphate (942 mg, 4.09 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed to perform a reaction for 7 hours.
[0181] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/chloroform=1/2) to give a pale yellow solid B-18 (520
mg, yield: 85%). Measurement by MALDl-MS demonstrated that M.sup.+
of this compound was found to be 744.
Synthesis Example 12
Synthesis of Exemplified Compound B-24
##STR00028##
[0183] In a 50-ml reaction vessel, XX-16 (559.5 mg, 1.13 mmol) and
2-isopropoxy-6-methoxyphenylboronic acid (771.0 mg, 3.67 mmol) were
mixed in a toluene/tetrahydrofuran (6 ml/4 ml) mixed solvent.
Dissolved oxygen was removed by nitrogen.
[0184] Next, Pd(OAc).sub.2 (6.7 mg, 0.03 mmol),
2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (S-Phos) (21.3 mg,
0.052 mmol), and tripotassium phosphate (1166.2 mg, 5.06 mmol) were
added thereto in a nitrogen atmosphere. The mixture was then heated
and refluxed at 110.degree. C. to perform a reaction for 8
hours.
[0185] The reaction solution was cooled to room temperature and
then concentrated under reduced pressure. Separation and
purification were performed by silica-gel chromatography (mobile
phase: hexane/ethyl acetate=4/1) to give a white solid power B-24
(545.8 mg, yield: 72.5%). Measurement by MALDl-MS demonstrated that
M.sup.+ of this compound was found to be 664.
Example 1
Electrochromic Properties
[0186] Each of the compounds described in the synthesis examples
was dissolved in chloroform. The absorption spectrum of each
solution in a neutral state (bleached state) was measured with an
ultraviolet and visible spectrophotometer (V-560, manufactured by
JASCO Corporation).
[0187] Measurement of the absorption spectrum at the time of
oxidation (colored) was performed as follows: a liquid in which the
compound described in the synthesis example was dissolved
(5.0.times.10.sup.-4 mol/L) in a dichloromethane solution of 0.1
mol/L tetrabutylammonium perchlorate, serving as a supporting
electrolyte, was subjected to constant potential oxidation at a
potential equal to or higher than the oxidation potential of the
compound using a working electrode composed of platinum, a counter
electrode composed of platinum, and a reference electrode composed
of silver, thereby measuring the absorption spectrum and the
transmittance spectrum changes.
[0188] Table 3 illustrates the results.
TABLE-US-00003 TABLE 3 Compound Bleached state Colored state No.
.lamda. max (nm) .lamda. max (nm) A-1 308.0 433.0 A-7 355.0 480.0
A-10 358.5 527.5 A-12 364.5 566.0 B-1 321.0 505.0 B-6 290.0 448.5
B-7 371.0 617.0 B-10 361.0 545.0 B-11 340.0 540.0 B-16 307.5 513.5
B-18 386.0 649.0 B-24 358.0 405.0
[0189] In any compound, in the neutral state, .lamda.max, at which
the absorption peak has the maximum intensity, is in the
ultraviolet region. There is no absorption in the entire visible
region. Thus, these compounds are transparent.
[0190] Furthermore, any colored species formed by oxidation
exhibited .lamda.max in the visible region and was visually
identified as being colored. The colored state due to oxidation was
returned to a colorless transparent state. Thus, electrochromic
properties associated with oxidation and reduction were
confirmed.
Example 2 and Comparative Example 1
Durable Stability of Organic EC Compound Against Redox Cycles-1
[0191] The durable stability of organic EC compounds A-1, A-7, and
A-10 according to the present invention and known compound Ref-1 as
Comparative Example 1 against redox cycles was evaluated. The
structural formula of Ref-1 is illustrated below.
##STR00029##
[0192] Compound Ref-1 according to Comparative Example 1 is
synthesized according to NPL 1 and is a compound that has
substantially no function of forming the steric hindrance of the
peripheral portion to the electrochromic portion because each of
the atoms of the peripheral portion and adjacent to the atom bonded
to the electrochromic portion has a hydrogen atom.
[0193] The electrochromic portion of this compound is composed of
dithienothiophene, and a phenyl group serves as the aromatic
ring.
[0194] Measurement of the durable stability against the redox
cycles was performed as follows: A liquid in which each compound
was dissolved (1.0.times.10.sup.-4 mol/L) in a dichloromethane
solution of 0.1 mol/L tetrabutylammonium perchlorate, serving as a
supporting electrolyte, was measured using a working electrode
composed of glassy carbon, a counter electrode composed of
platinum, and a reference electrode composed of silver.
[0195] A rectangular-wave potential program was repeatedly applied
to the solution, the rectangular-wave potential program including
constant potential oxidation at a potential equal to or higher than
the oxidation potential of the compound for 10 seconds and constant
potential reduction at 0 V (vs. Ag/Ag.sup.+) for 10 seconds. Cyclic
voltammetry (CV) measurement was performed at every 100 redox
cycles. FIG. 2 illustrates a change in oxidation potential
associated with the number of redox cycles.
[0196] In compound Ref-1 according to Comparative Example 1, the
oxidation potential started to shift to higher potentials after
about 1400 redox cycles. After 3000 cycles, the oxidation potential
was increased to about 1.25 times, which indicated the degradation
of the compound.
[0197] In contrast, for compounds A-7 and A-10 according to the
present invention, substantially no change in oxidation potential
was observed even after 3000 redox cycles.
[0198] Thus, A-7 and A-10 have high durability, compared with
Ref-1. This is probably because in the compounds according to the
present invention, the substituents on the aromatic ring protect
the electrochromic portion. That is, other organic EC compounds
according to this embodiment also have high durability.
[0199] With respect to the durable stability of compound A-1, the
amount of the change in oxidation potential was intermediate
between Ref-1 and either A-7 or A-10. The methyl groups on the
aromatic rings each have a relatively weak function of forming
steric hindrance. Thus, the excluded volume effect is provided to
some extent, compared with Ref-1.
Example 3 and Comparative Example 2
Durable Stability of Organic EC Compound Against Redox Cycles-2
[0200] The durable stability of organic EC organic compounds A-7,
A-10, A-12, B-1, B-6, B-10, B-16, and B-18 according to this
embodiment and known compounds Ref-1, Ref-2, and Ref-3 as
Comparative Example 2 against redox cycles was evaluated. The
structural formulae of Ref-2 and Ref-3 are illustrated below.
##STR00030##
[0201] Compound Ref-2 according to the comparative example is a
compound without a peripheral portion. Compound Ref-3 is a known
organic EC compound (diethylviologen diperchlorate) that is colored
by reduction.
[0202] In this example, measurement of the durable stability
against the redox cycles was performed as follows: A solution and a
measuring system the same as those in Example 2 were used. A
rectangular-wave potential program was repeated 20,000 cycles, the
rectangular-wave potential program including constant potential
oxidation at a potential equal to or higher than the oxidation
potential of the compound for 10 seconds and constant potential
reduction at 0 V (vs. Ag/Ag.sup.+) for 10 seconds.
[0203] Cyclic voltammetry (CV) measurement was performed at every
100 redox cycles. The number of redox cycles at the time of a 20%
or more change in oxidation peak current was defined as the number
of durable redox cycles. Note that the number of durable redox
cycles of a compound in which a change in current after 20,000
cycles was within 20% was defined as 20,000 cycles.
[0204] FIG. 3 is a graph illustrating the number of durable redox
cycles plotted against the projected molecular length of the
peripheral portion.
[0205] Here, the projected molecular length of the peripheral
portion indicates the projected molecular length of a molecular
structure determined by structural optimization calculations in a
ground state using the electronic state calculation software,
Gaussian 03* Revision D. 01, and serves as an indicator of the
function of forming steric hindrance against the conjugated plane
of the electrochromic portion.
[0206] Compound Ref-2 according to the comparative example was
subjected to electrolytic polymerization immediately after the
application of a voltage and thus did not have redox stability as a
compound.
[0207] For compounds Ref-1 and Ref-3 that lack the function of
protecting the electrochromic portion, the function being provided
by the substituent on the peripheral portion, the numbers of
durable cycles of Ref-1 and Ref-3 were 1500 and 1600 cycles,
respectively, which were low in durable redox stability.
[0208] In contrast, in the case of any of the organic EC compounds
according to this embodiment, the durable redox stability exhibited
10,000 cycles or more even when the electrochromic portion had
various chemical structures.
[0209] In the organic EC compound according to this embodiment, the
projected molecular length of the substituent on the peripheral
portion is 7 .ANG. or more. The electrochromic portion is
sterically protected by the effect of a large excluded volume of
the substituent on the peripheral portion.
Example 4
Production of EC Device
[0210] Lithium perchlorate serving as a supporting electrolyte was
dissolved in propylene carbonate in a concentration of 0.1 M. Then
B-7, which is an organic EC compound according to the present
invention, was dissolved therein in a concentration of 20.0 mM,
thereby preparing an EC medium.
[0211] An insulating layer (SiO.sub.2) was formed on the peripheral
part of a glass substrate (lower electrode) provided with a
transparent conductive film (ITO) while an opening that defines a
coloring-bleaching region was left. A PET film (Melinex S
(registered trademark), manufactured by Teijin DuPont Films Japan
Limited) that defines a distance between substrates was held by a
glass substrate (upper electrode) provided with a transparent
conductive film. The peripheral part of the device was sealed with
an epoxy-based adhesive while an opening for injecting the EC
medium was left, thereby producing an empty cell provided with the
inlet.
[0212] The thickness of the film was used as the distance between
the pair of electrodes of the device according to the present
invention. Empty cells having different interelectrode distances
were produced using films having different thicknesses.
[0213] Next, the foregoing EC medium was injected from the opening
of the device by a vacuum injection method. The opening was sealed
with the epoxy-based adhesive in the same way as the peripheral
part, thereby producing an EC device.
[0214] The device according to this example has a device structure
(unipolar-type device) in which the anodically EC organic compound
is colored on one electrode by oxidation.
[0215] <EC Properties of Unipolar-Type Device>
[0216] Electrochromic properties of the device having an
interelectrode distance of 60 .mu.m were evaluated. This EC device
immediately after the production had a transmittance of 80% or more
throughout the visible range and thus had high transmittance.
[0217] When a voltage of 2.2 V was applied to the device, the
device exhibited absorption (506 nm) originating from the oxidized
species of compound B-7 and was colored. At the absorption
wavelength (506 nm), the coloration efficiency was 473 cm.sup.2/C.
Furthermore, the device was bleached by the application of a
voltage of -0.5 V and exhibited reversible coloring-bleaching
behavior.
Example 5
EC Properties of Unipolar-Type Device
[0218] A device was produced as in Example 4, except that 5.0 mM of
B-24, which is an anodically EC organic compound, was used as the
organic EC compound in the EC medium and that FTO was used as the
electrode substrates. The resulting unipolar-type device had an
interelectrode distance of 70 .mu.m.
[0219] When a voltage of 3.4 V was applied to the device, the
device exhibited absorption (388 nm) originating from the oxidized
species of compound B-24. At the absorption wavelength (388 nm),
the coloration efficiency was 1041 cm.sup.2/C.
Example 6
EC Properties of Bipolar-Type Device
[0220] A device was produced as in Example 4, except that 30.0 mM
of B-7, which is an anodically EC organic compound, and 30.0 mM of
Ref-3, which is a cathodically EC organic compound, were used as
the organic EC compound in the EC medium, tetrabutylammonium
perchlorate (0.1 M) was used as the supporting electrolyte, and
that FTO was used as the electrode substrates.
[0221] The device according to this example has a device structure
(bipolar-type device) in which the anodically EC organic compound
is colored on one electrode by oxidation and the cathodically EC
organic compound is colored on the counter electrode by
reduction.
[0222] Electrochromic properties of the device having an
interelectrode distance of 60 .mu.m were evaluated. This EC device
immediately after the production had a transmittance of 80% or more
throughout the visible range and thus had high transmittance.
[0223] When a voltage of 1.4 V was applied to the device, the
device exhibited absorption (506 nm) originating from the oxidized
species of compound B-7 and absorption (604 nm) originating from
the reduced species of compound Ref-3, and was colored. At the
absorption wavelength (506 nm) originating from the oxidized
species of the anodically EC organic compound, the coloration
efficiency was 470 cm.sup.2/C. Furthermore, the device was bleached
by the application of a voltage of -0.5 V and exhibited reversible
coloring-bleaching behavior.
Example 7
Durable Stability of EC Device Against Redox Cycles
[0224] A device was produced as in Example 4, except that 6.0 mM of
A-12, which is an anodically EC organic compound, was used as the
organic EC compound in the EC medium. The resulting unipolar-type
device had an interelectrode distance of 150 .mu.m. When a voltage
of 2.3 V was applied to the device, the device exhibited absorption
(498 nm) originating from the oxidized species of compound A-12 and
was colored.
[0225] At the absorption wavelength (498 nm), the coloration
efficiency was 1058 cm.sup.2/C. Furthermore, the device was
bleached by the application of a voltage of -0.5 V and exhibited
reversible coloring-bleaching behavior. Next, the durable stability
of the EC device against redox cycles was measured.
[0226] A triangular wave (electric potential gradient: 200 mV/sec)
with peak values of 2.3 V and -0.5 V was repeatedly applied to the
EC device according to this example. The EC device exhibited
satisfactory coloring-bleaching behavior even after 800 redox
cycles.
Example 8
Durable Stability of EC Device against Redox Cycles
[0227] A device was produced as in Example 4, except that 6.0 mM of
B-16, which is an anodically EC organic compound, was used as the
organic EC compound in the EC medium and was dissolved to prepare
an EC medium. The resulting unipolar-type device had an
interelectrode distance of 150 .mu.m.
[0228] When a voltage of 2.6 V was applied to the device, the
device exhibited absorption (528 nm) originating from the oxidized
species of compound B-16 and was colored.
[0229] At the absorption wavelength (528 nm), the coloration
efficiency was 240 cm.sup.2/C. Furthermore, the device was bleached
by the application of a voltage of -0.5 V and exhibited reversible
coloring-bleaching behavior.
[0230] A triangular wave (electric potential gradient: 200 mV/sec)
with peak values of 2.6 V and -0.5 V was repeatedly applied to the
EC device according to this example. The EC device exhibited
satisfactory coloring-bleaching behavior even after 1000 redox
cycles.
Example 9
Durable Stability of EC Device Against Redox Cycles
[0231] A device was produced as in Example 4, except that 6.0 mM of
A-12, which is an anodically EC organic compound, and 6.0 mM of
Ref-3, which is a cathodically EC organic compound, were used as
the organic EC compound in the EC medium. The resulting
bipolar-type device had an interelectrode distance of 150
.mu.m.
[0232] When a voltage of 1.7 V was applied to the device, the
device exhibited absorption (498 nm) originating from the oxidized
species of compound A-12 and absorption (604 nm) originating from
the reduced species of compound Ref-3, and was colored.
Furthermore, the device was bleached by the application of a
voltage of -0.5 V and exhibited reversible coloring-bleaching
behavior.
[0233] A triangular wave (electric potential gradient: 200 mV/sec)
with peak values of 1.7 V and -0.5 V was repeatedly applied to the
EC device according to this example. The EC device exhibited
satisfactory coloring-bleaching behavior even after 1600 redox
cycles.
Example 10
Bleaching Response Speed
[0234] Bipolar-type devices having three types of interelectrode
distances (60 .mu.m, 150 .mu.m, and 350 .mu.m) were produced using
the EC medium (anodically EC organic compound: 6.0 mM of
A-12/cathodically EC organic compound: 6.0 mM of Ref-3) prepared in
Example 9. The response time needed to bleach each device was
measured.
[0235] The bleaching response time in this example indicates the
length of time needed to change the optical density from 0.9 (12.5%
of the initial transmittance) to 0.02 (95% of the initial
transmittance).
[0236] FIG. 4 is a graph illustrating the relationship between the
interelectrode distance and the bleaching response speed. At an
interelectrode distance of 350 .mu.m, the response time was 31.4
seconds. In contrast, in the case of the device having an
interelectrode distance of 150 .mu.m, the response time was 6.8
seconds. In the case of the device having an interelectrode
distance of 60 .mu.m, the response time was 2.0 seconds. That is, a
reduction in interelectrode distance resulted in significantly
satisfactory bleaching response speed.
[0237] The solid line in FIG. 4 is a plot of data estimated from
the three-point data.
[0238] As described above, it is possible to provide the EC device
according to the present invention, the EC device having high
durable stability against redox cycles, high transparency in the
bleached state, i.e., the EC device does not absorb light in the
visible region in the bleached state, and having excellent response
speed.
[0239] The present invention is not limited to the foregoing
embodiments. Various changes and modifications may be made without
departing from the spirit and scope of the invention. Therefore,
the following claims are appended to make public the scope of the
invention.
[0240] According to the present invention, it is possible to
provide an EC device having high durability, a high response speed,
and high transparency when the device is bleached.
[0241] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
* * * * *